1. Field of the Invention
The present invention relates to the technical field of General Packet Radio Service (GPRS) and, more particularly, to a method and a system for applying a multi-protocol label switching network in general packet radio service.
2. Description of Related Art
GPRS is defined in the standard of Global System for Mobile communication (GSM) phase 2+ for providing transmission service of packet switching, which utilizes the technique of packet mode to transmit data and control message in GSM network at a rate of approximately 120 kbps. FIG. 1 shows a GPRS core network 10 and its architecture, while FIG. 2 shows the signalling plane and transmission plane at the Gn interface of the GPRS architecture, which are five-layer and six-layer structures, respectively.
Because GPRS architecture clearly distinguishes the wireless sub-network and wired sub-network, the backbone network formed by the wired sub-network can be constructed by repeatedly utilizing the existing network architecture, such as the Internet, or new network architecture, such as Multiple Protocol Label Switching (MPLS). Such a method of distinguishing wireless sub-networks and wired sub-networks is accomplished by two newly defined network nodes, which are the Serving GPRS Support Node 12 (SGSN) connected to the base station of the wireless network, and the Gateway GPRS Support Node 13 (GGSN) connected to the external packet switching network 15. SGSN 12 is responsible for tracing and managing the position of a Mobile Station 14 (MS), performing the functions of verification, scheduling and medium access control in packet transmission. GGSN 13 is responsible for routing to the external packet switching network 15 to exchange packets, and utilizing the IP-based GPRS backbone 11 to communicate with the SGSN 12.
For a specific MS 14, GGSN 13 can use IP tunneling techniques to establish a dedicated communicating tunnel particularly between SGSNs 12 that the MS 14 belongs to, such that the MS 14 can access data of the external packet switching network 15. The establishment of this dedicated communicating tunnel and its location and verification information are accomplished by a PDP context activation procedure. This procedure will establish related PDP context tables in MS 14, SGSN 12 and GGSN 13, respectively, for storing information related to the communicating tunnel, mobile station identification and verification, wherein the PDP context tables in SGSN/GGSN are stored with the IP addresses of the GGSN/SGSN corresponding to the two ends of the communicating tunnels. In addition, the GPRS Tunneling Protocol (GTP) in the GPRS protocol defines the GPRS control messages, including control messages related to the PDP context activation procedure, and also defines the packet format and GTP header of the data packet in using IP tunnel techniques. The GTP header includes a set of Tunnel IDs (TIDs) for use by SGSN to identify a specific mobile station in the wireless sub-network.
As GPRS backbone network uses IP tunnel techniques to establish a dedicated communicating tunnel between GGSN 13 and SGSN 12, MS 14 is able to access data of the external packet switching network 15. However, such a technique also results in drawbacks such as increasing the length of the packet header, increasing the IP route delay and difficulty in supporting the quality of service. These drawbacks severely influence the GPRS backbone network transmission efficiency. Therefore, it is desirable for improvements in the above conventional GPRS architecture.